The present invention relates to a heater based on a hot radiant plate which radiates heat, and comprising a heating element which produces and distributes heat across the radiant plate, a thermal insulation layer which also supports the radiant plate and ensures good heat contact between the heating element and the radiant plate, a cold plate where the electrical and mechanical fastening means are mounted, and fastening means between the hot plate and the cold plate which, with minimal heat contact, ensure free horizontal movement between the two plates while keeping them locked together about a center point.
A radiant panel heater is in principle based on heating a plate to a desired temperature so that heat waves are emitted to the surroundings as direct radiation from the plate. As a rule it is desirable to direct the heat waves in particular directions, for example downward from a ceiling heater, this being achieved by thermal insulation in other directions or by shielding against radiation in those directions where it is unwanted.
Electric radiant heaters for ceilings are previously known, comprising a relatively elongate radiant heating element consisting of an extruded aluminum profile which is heated to about 300.degree. C. The radiant heat profile is mounted in a steel box and insulation is placed on the top side so that there is a significant temperature difference between the radiating plate and the surface of the radiant element facing other directions.
Because of the various types of requirements set for such electric radiant heaters for ceilings, the design thereof involves considerable difficulties, inter alia, caused by uneven thermal expansion of the materials contained in the structure, an expansion which may lead to undesirable sounds, torsion and deformations. Furthermore, in the previously known examples there is considerable heat contact and thereby heat transfer to those parts of the heater which shall not emit radiant heat, this heat thus being unavailable for heating those areas which are meant to be heated. It is only the radiant heat energy emitted in the desired direction that can be regarded as effective energy; all other radiated energy is to be considered a heat loss.
A ceiling heater is always highly visible in a room and should therefore be as discreet in its design and selection of materials as possible so as not to become a disturbing element in the ceiling, this being particularly important in buildings such as churches, for example. It may often be desirable to design the ceiling heater as a part of the ceiling, a task rendered difficult with the existing structures which are fixedly locked to one or more aluminum profiles positioned side by side in a steel box.
For space heating it is generally these types of heaters that are used:
Wall radiators, the main purpose of which is to heat the air in the room. These are well suited to low-ceilinged rooms used for extended periods of time. This type of heating is not suited to high-ceilinged rooms because a great deal of air circulation will occur in the room, at the same time as the hot air will accumulate on top, next to the ceiling.
Ceiling heat and floor heat, both of which are a low-temperature radiant heat having a surface temperature 5.degree.-25.degree. C. above the air temperature. Here the purpose is to give a low temperature radiant heat to the whole room from the heating elements built into the ceiling or floor. The weakness of the system is that it has a great deal of thermo-technical inertia, and that it does not concentrate the heat in those areas of the room where it is wanted. The effect delivered is about 150 watt/m.sup.2.
Reflector heaters, which have incandescent heating elements of 600.degree.-800.degree. C. These are heaters which have high heat output in relation to size. They emit a short-wave heat radiation which after an extended period of time may often feel uncomfortable. The reflector is easily soiled, preventing the heat waves from being reflected down into the room and resulting in the heater changing character by approaching a convector heater, the heat thereby remaining on top right next to the ceiling.
Medium-temperature radiant panel heaters, which may be ceiling heater cassettes, either free-hanging or built into dropped ceiling systems, and having a radiant plate temperature in the range of 50.degree.-100.degree. C. above air temperature. For higher temperatures (up to 330.degree. C.) the radiant plate is commonly an extruded aluminum profile having the heating element positioned in a track in the aluminum profile which is mounted in an outer housing, so that the heat expansion in the longitudinal direction can occur as unobstructed as possible (Norwegian Patent Application No. 873830). These heaters have little thermo-technical inertia, function equally well if they become soiled, and are particularly well suited to high-ceilinged rooms which have poor thermal insulation in the walls and are not in continuous use. They provide a comfortable long-wave radiant heat which can be concentrated over those areas in the room where heating is desired, and they do not produce much air circulation in the room. These are heaters yielding an effect of 500-5000 watt/.sup.2.